I've found a few parts and pieces for the same reason. My dad gave me his old Rohm 38S. The grips are crap and it was missing screws but here's what I found.
Grips:
http://www.midwayusa.com/product/243770/vintage-gun-grips-rohm-gmbh-sontheim-385-38-special-polymer-black
I didn't buy these but they look pretty darn close. These dont' come with screws though. (LAME)
Screws:
https://www.gunpartscorp.com/catalog/Products.aspx?catid=8741
I think you'll need #61 and #70 screws from this scematic.
I bought 2 each of these and I haven't gotten them yet (maybe today).
The gun my dad gave me had 2 out of I think the 3 screws it needed so I may have extra after I get these.
You may also find stuff here as well.
http://www.gun-parts.com/rohm/
I know lots of people say this is a crap gun and although it's cheaply made it is still a gun and guarantee you still don't want to be in front of it. I've shot about 150 rounds through it and had no issues. This is also after it had sat in a drawer for years and years and I honestly think it was never cleaned from the first moment my dad had it. That's the way I shot it and it was fine. The trigger pull is stupid tough and no amount of oil or cleaning I've done has helped it.
I don't tihnk getting rid of it would be worth the few dollars you'd get for it. Keep it and make it functional and use it as a barter gun when the zombies invade.